Conventionally, alpine ski boots practice in the filed alpine ski boots calls for equipping these boots are provided with various tightening devices which are generally intended to eliminate, or at least markedly reduce, the play between the lower part of the leg or the foot of a skier and the boot worn by the skier. Devices may be provided, most notably, to tighten the upper around the lower part of the skier's leg, or to secure the foot inside the lower part of the shell. Known tightening mechanisms generally comprise a flexible connector, such as a wire, cable, or strap, one of whose ends is hooked onto a movable tension lever mounted on a base fastened on an appropriate part of the boot. The tension lever can be moved to a closed position in which it is flattened on its base and keeps the flexible connector under tension, this position corresponding to the desired level of tightness, or to an open position in which the lever is drawn away from its base and the flexible connector is relaxed, this arrangement corresponding to the loosened position. In most tightening devices of this kind, the lever is jointed onto the base about an axis, so that the lever and the base constitute a unit. This type of construction is not entirely satisfactory, since it does not provide every possible assurance of safety; in fact, in the open position, the tension lever forms an outwardly-extending angle with its base, and thus projects outward from the wall of the surrounding boot to which it is attached, in such a way that it can be damaged or torn off when it collides with an obstacle.
To overcome this difficulty, tightening devices are known in which the tension lever is "free" and is, in the closed position, kept pressed against a stop solely under the effect of the tension of the flexible connector. A tightening device of this kind is described, for example, in CH-614358 and FR-A-2 373 981. Because of this simple support arrangement, the tension lever can, when projecting outward, be easily ejected from the stop holding it, thereby making it possible to very appreciably reduce the risks that the lever will be damaged or torn away.